The present invention relates generally to ground opener units for an agricultural implement and, more particularly, to an assembly for adjusting the packing pressure applied by a trailing packer wheel of a disc opener unit.
One type of planting implement is commonly equipped with one or more rows of discs or coulters carried by a tool bar, commonly referred to as a disc drill, which is towed by a tractor. Typically, an air cart, which holds seed and/or fertilizer, is also towed by the tractor and pneumatically supplies the individual disc openers with seed and/or fertilizer. The disc openers are attached to the disc drill frame by individualized arms or linkages which allow the disc openers to operate independently of another. This “independence” allows the discs to independently respond to changes in terrain and field obstructions.
Each disc has a generally flat construction that is rotated a few degrees, e.g., 7 degrees, about a vertical axis so that as the disc is pulled through the soil the leading surface of the disc displaces soil and creates a furrow in the soil. Downward pressure on the disc is provided by a spring or hydraulic cylinder to hold the disc at a desired furrowing depth, e.g., desired seeding depth. The depth at which the disc cuts the furrow into the soil is controlled by a gauge wheel that runs in relative close proximity to the disc. In addition to its depth controlling function, for some disc drills, the placement of the gauge wheel close to the disc also assists in keeping the disc surface clean of soil, mud, or debris buildup. Also, the gauge wheel rides over the soil displaced by the disc as the furrow is being cut to prevent the displaced soil from being thrown.
The disc cuts a furrow or trench in the soil into which seed and/or fertilizer is deposited. The seed and/or fertilizer is dropped through a tube into the trench, and the disc holds the trench open on one side and a disc scraper blade holds it open on the opposite side. The trench walls then collapse onto the seed and/or fertilizer when the disc and scraper blade pass. A trailing wheel then packs the soil atop the seed and/or fertilizer.
Most disc drills include a torsion spring that is used to bias the trailing (packer) wheel against the field or planting surface. While generally effective in holding the packer wheel down against the planting surface, such torsion springs are generally unable to create high packing forces, such as those greater than 100 lbs. Additionally, for many disc drills, the placement of the torsion spring is such that the spring is prone to collect field trash and other debris.